Basal Cell Carcinoma Tumor Research Articles

Prolonged Prevention of Squamous Cell Carcinoma of the Skin by Regular Sunscreen Use

Half of all cancers in the United States are skin cancers. We have previously shown in a 4.5-year randomized controlled trial in an Australian community that squamous cell carcinomas (SCC) but not basal cell carcinomas (BCC) can be prevented by regular sunscreen application to the head, neck, hands, and forearms. Since cessation of the trial, we have followed participants for a further 8 years to evaluate possible latency of preventive effect on BCCs and SCCs. After prolonged follow-up, BCC tumor rates tended to decrease but not significantly in people formerly randomized to daily sunscreen use compared with those not applying sunscreen daily. By contrast, corresponding SCC tumor rates were significantly decreased by almost 40% during the entire follow-up period (rate ratio, 0.62; 95% confidence interval, 0.38-0.99). Regular application of sunscreen has prolonged preventive effects on SCC but with no clear benefit in reducing BCC.

Basal Cell Carcinoma of Scalp in Patients With History of Childhood Therapeutic Radiation

Basal cell carcinoma (BCC) is the most common human malignant neoplasm. Some patients with scalp BCC have had a history of childhood scalp radiation for the treatment of tinea capitis. It is not clear whether BCC in these cases has a more aggressive nature and requires a more aggressive resection. We performed a retrospective study to compare BCC tumor specification and treatment results between irradiated and nonirradiated patients. From 1995 to 2005, a total of 74 patients were diagnosed with scalp BCC. Thirty-eight patients (group A) had a history of childhood radiation to the scalp for the treatment of tinea capitis, and the other 36 (group B) did not. We compared these 2 groups in 16 different parameters, which included general information (age, sex), disease history (time interval from onset of lesion to the first office visit, number of admissions, total length of hospital stay), tumor specifications (number of primary lesions, invasion depth, histologic subtypes, location), surgical history (number of operations in our center and other hospitals, type of surgical treatment, margins of resection), recurrences, new lesions, and metastasis. Statistical analysis was performed using SPSS 13.0 software. No significant difference in gender and age was observed between the 2 groups (P = 0.06 and P = 0.35, respectively). Patients in group A had a longer history of scalp lesions (P = 0.001). They also had more hospital admissions (P = 0.008) and operations (P = 0.01) in our center, with a longer period of hospitalization (P = 0.01). Mean number of primary lesions, the location of tumor, and the depth of invasion did not differ significantly between the 2 groups (P = 0.34, P = 0.78, and P = 0.73, respectively). There was no meaningful difference in safe resection margin for the first lesion between the 2 groups (P = 0.27); however, the number of recurrent lesions was significantly higher in group A (P = 0.003). Also, need for more aggressive resection and more complicated reconstruction was more in group A patients (P = 0.01 and P = 0.015, respectively). Only in group A new lesions and metastasis were found. BCC in irradiated scalp has a more aggressive behavior and may need a more aggressive surgical resection. Also, these patients should be under close observation because there is a higher chance for tumor recurrence and also new lesions occurring elsewhere in the scalp.

Bone morphogenetic protein antagonist gremlin 1 is widely expressed by cancer-associated stromal cells and can promote tumor cell proliferation

Although tissue microenvironments play critical roles in epithelial development and tumorigenesis, the factors mediating these effects are poorly understood. In this work, we used a genomic approach to identify factors produced by cells in the microenvironment of basal cell carcinoma (BCC) of the skin, one of the most common human cancers. The global gene expression programs of stromal cell cultures derived from human BCCs showed consistent, systematic differences from those derived from nontumor skin. The gene most consistently expressed at a higher level in BCC tumor stromal cells compared with those from nontumor skin was GREMLIN 1, which encodes a secreted antagonist of the bone morphogenetic protein (BMP) pathway. BMPs and their antagonists are known to play a crucial role in stem and progenitor cell biology as regulators of the balance between expansion and differentiation. Consistent with the hypothesis that BMP antagonists might have a similar role in cancer, we found GREMLIN 1 expression in the stroma of human BCC tumors but not in normal skin in vivo. Furthermore, BMP 2 and 4 are expressed by BCC cells. Ex vivo, BMP inhibits, and Gremlin 1 promotes, proliferation of cultured BCC cells. We further found that GREMLIN 1 is expressed by stromal cells in many carcinomas but not in the corresponding normal tissue counterparts that we examined. Our data suggest that BMP antagonists may be important constituents of tumor stroma, providing a favorable microenvironment for cancer cell survival and expansion in many cancers.

Basal Cell Carcinoma Progression Correlates With Host Immune Response and Stromal Alterations: A Histologic Analysis

Neoplastic progression is characterized in part by escape from immune surveillance and formation of growth-permissive stroma. Basal cell carcinoma (BCC) can be subclassified into low- and high-risk types for local recurrence. To determine whether these types of BCC correlate with alterations in local host immune response and stroma and whether these changes follow stepwise histologic progression from low- to high-risk subtypes, we assessed the clinicopathologic features in 175 consecutive primary (nonrecurrent) BCC excision specimens. BCCs exhibited a significantly higher frequency of mixed rather than homogeneous growth patterns (76% vs. 24%, P=0.0001). Nodular (84%) was the most common pattern identified followed by superficial (77%), infiltrative (27%), morpheic (5%) and micronodular patterns (4%). Only superficial (12% of all BCC) and nodular (12%) patterns were identified in BCC with a homogeneous histologic phenotype. Micronodular and infiltrative-morpheic patterns were not identified together in mixed patterned BCCs, and these high-risk types were contiguous with nodular BCC. Superficial predominant BCC (major growth pattern) was significantly associated with trunk and extremity location (76%) and skin without solar elastosis (82%), whereas BCC harboring a nodular growth pattern component was significantly associated with a head and neck location (63%) and the presence of adjacent solar elastosis (all P< or =0.03). Significant correlations were identified for BCC subtypes with inflammatory and stromal alterations: superficial BCC with old regression and moderate to dense peritumoral lymphocytic infiltrates; high-risk types correlated with active regression; infiltrative and morpheic BCC with fibrosing tumor stroma; and micronodular BCC with loss of both host inflammatory and stromal tumor responses. Evaluating the theoretical histologic stepwise model of BCC progression (superficial-to-nodular-to-micronodular, or superficial-to-nodular-to-infiltrative-to-morpheic BCC types) revealed significant linear correlations with host response and alterations of tumor stroma (r=0.54, P=0.0001). BCC exhibit distinct epithelial-stromal-inflammatory patterns that correlate with BCC subtype and tumor progression. This ostensible pathway of diminishing host response and gain of permissive tissue environment highlights neoplastic evolution from low to high risk for local recurrence of BCC and implicates a histologic continuum reflecting dynamic host-BCC interactions.

Long‐term establishment, characterization and manipulation of cell lines from mouse basal cell carcinoma tumors

There have been few reports of successful long-term culture of cells established from cutaneous basal cell carcinoma (BCC) tumors. Here, we describe techniques that have enabled us to establish three long-term cultures of BCC cells isolated from BCC tumors that arose in irradiated Patched 1 (Ptch1)(+/-) mice. All three cell lines showed cellular morphology similar to that of BCC tumors and could be propagated for at least 20 passages. In addition, similar to BCC tumors, all cell lines had lost the wildtype Ptch1 allele, expressed BCC molecular markers, and responded similarly to cyclopamine, a small molecule inhibitor of Hedgehog signaling. Finally, we describe an efficient electroporation technique for DNA transfection into the BCC cell lines and show that they have activated Hedgehog signaling activity, albeit at a level lower than that of murine BCCs in vivo. These data indicate that the cell lines are bona fide long-term cultures of BCC cells and that DNA plasmids can be introduced into the BCC cell lines with relatively high transfection efficiency using a modified electroporation technique.

Expression of the apoptosis-suppressing protein Bcl-2 in non-melanoma skin cancer.

Basal cell carcinoma (BCC) is typically a slow-growing malignant tumour, composed of cells similar to those in the basal area of the epidermis. We investigated the expression of bcl-2 (B-cell leukaemia/lymphoma-2) in BCC, and also in squamous cell carcinoma (SCC) of the skin. The proto-oncogene bcl-2 encodes a protein which inhibits programmed cell death (apoptosis). The protein is expressed in basal cells in normal human epithelium, but not in the suprabasal cell layers. Immunohistochemical localization using a monoclonal anti-Bcl-2 antibody revealed bcl-2 expression in all the BCCs (15 patients). SCCs did not express bcl-2 (five patients). The positive Bcl-2 staining of BCC tumour cells supports the hypothesis that BCCs originate from the basal layer of the epidermis. The bcl-2 expression of BCC tumour cells also suggests a neoplastic transformation caused by extended cell survival rather than increased cell proliferation. This type of neoplastic growth is possibly associated with less aggressive tumour behaviour.

Second Malignant Neoplasms Following the Treatment of Brain Tumors in Children

We investigated retrospectively 992 children with central nervous system tumors who were treated at our center between 1970 and 2004. All of the patients were treated by surgery, chemotherapy, and/or radiotherapy. Six patients developed second malignant neoplasms, and their clinical and histopathologic characteristics are reviewed in this article. The second malignant neoplasms were diagnosed as non-Hodgkin lymphoma, myelodysplastic syndrome, basal cell carcinoma, malignant melanoma, Kaposi sarcoma, and high-grade neuroectodermal tumor. The initial diagnoses were ependymoblastoma in one, medulloblastoma in three, and low-grade astrocytoma in two patients. The median latency time was 3.03 years (range 0.39-22.93 years). The outcome varied according to the histopathologic type of the second tumor. The patients who developed non-Hodgkin lymphoma and myelodysplastic syndrome died of progressive disease. The patients with second skin neoplasms are alive as of the time of this writing. The patient with Kaposi sarcoma developed one of the rare reported second malignant neoplasms following a primary brain tumor in childhood. A wide spectrum of second malignant neoplasms was detected after treatment of primary brain tumors with surgery, radiotherapy, and chemotherapy. Long-term follow-up is therefore necessary for the child who has survived a primary central nervous system tumor.

Recurrent NMYC copy number gain and high protein expression in basal cell carcinoma

Formation of basal cell carcinoma (BCC) has been linked to deregulation in the sonic hedgehogh (Shh) signalling pathway. Though mutations of the genes, PTCH1 and SMO, are known to be involved in aberrant Shh signalling, the distinct downstream effectors of these genes are poorly described. Studies have indicated that the NMYC oncogene is a potential Shh downstream effector. To assess the expression of Nmyc protein and gene copy numbers of the NMYC gene locus in a representative BCC tumour collection, immunohistochemistry (IHC) and fluorescence in situ hybridisation (FISH) were performed on 273 BCC specimens of different growth patterns and anatomic localisations on tissue microarray (TMA) sections. High Nmyc protein expression was detected in 72.7% (160/220) of all BCC specimens. Strong Nmyc immunopositivity was more frequently found in infiltrative BCCs compared to nodular/superficial BCCs (p=0.005), and in BCCs of the head compared to BCCs of other anatomic localisations (p=0.021). The prevalence of NMYC copy number gains was 17.5% (37/211), including three tumours with nodular differentiation that exhibited a distinct high-level amplification of the NMYC locus. These data indicate that high expression of the Shh downstream mediator, Nmyc, is a frequent event in BCC, predominantly in more aggressive subtypes. Although the NMYC copy number gain found in a subset of cases might contribute to this aberrant Nmyc protein expression by a gene dosage effect, our data suggests that Nmyc protein can also be induced by aberrant Shh signalling, acting as an effector molecule of the Shh pathway. Novel systemic anti-sense NMYC inhibition strategies could be a promising option for therapy-refractory BCC.

Microarray profiles of human basal cell carcinoma: Insights into tumor growth and behavior

Basal cell carcinoma (BCC) is the most common human neoplasm. Much interest lies in determining the genetic basis of BCC to explain the unique locally invasive phenotype and infrequent metastatic behavior of these skin tumors. We sought to examine a gene expression profile for BCC to elucidate new molecules responsible for its unique growth characteristics. We analyzed gene expression patterns of 50 BCC tumors using spotted cDNA microarrays of 1718 characterized human genes related to cancer and immunity. This is the largest and most comprehensive gene expression study ever performed for BCC. Nodular and sclerosing histological subtypes of BCC were examined and compared to normal control skin. After statistical filtering, 374 significantly dysregulated genes were sorted by hierarchical clustering to determine trends of gene expression and similarities between patient gene expression profiles. A total of 165 upregulated genes and 115 downregulated genes were identified. These covered a range of categories, including extracellular matrix, cell junctions, motility, metastasis, oncogenes, tumor suppressors, DNA repair, cell cycle, immune regulation and angiogenesis. Clusters of genes were either commonly dysregulated across the 50 patient sample, or selectively affected in subsets of tumors. Histological subtypes were not distinguishable by hierarchical clustering. Many of the genes elucidated, including collagen type IV subunits and other novel candidates, possess functions related to extracellular matrix remodeling and metastasis. These results suggest a gene profile which may explain the invasive growth yet rarely metastatic behavior of BCC. The genes identified may also be potential targets for therapeutics aimed at further controlling invasiveness and local destruction of BCC.

Repeated Occurrence of Basal Cell Carcinoma of the Skin and Multifailure Survival Analysis: Follow-up Data from the Nambour Skin Cancer Prevention Trial

The aim of this study was to apply multifailure survival methods to analyze time to multiple occurrences of basal cell carcinoma (BCC). Data from 4.5 years of follow-up in a randomized controlled trial, the Nambour Skin Cancer Prevention Trial (1992-1996), to evaluate skin cancer prevention were used to assess the influence of sunscreen application on the time to first BCC and the time to subsequent BCCs. Three different approaches of time to ordered multiple events were applied and compared: the Andersen-Gill, Wei-Lin-Weissfeld, and Prentice-Williams-Peterson models. Robust variance estimation approaches were used for all multifailure survival models. Sunscreen treatment was not associated with time to first occurrence of a BCC (hazard ratio = 1.04, 95% confidence interval: 0.79, 1.45). Time to subsequent BCC tumors using the Andersen-Gill model resulted in a lower estimated hazard among the daily sunscreen application group, although statistical significance was not reached (hazard ratio = 0.82, 95% confidence interval: 0.59, 1.15). Similarly, both the Wei-Lin-Weissfeld marginal-hazards and the Prentice-Williams-Peterson gap-time models revealed trends toward a lower risk of subsequent BCC tumors among the sunscreen intervention group. These results demonstrate the importance of conducting multiple-event analysis for recurring events, as risk factors for a single event may differ from those where repeated events are considered.

Nucleolar organizer region staining patterns in paraffin‐embedded tissue cells from human skin cancers

Increased number of nucleoli (nucleolar organizer regions, NORs) with abnormal shapes and sizes, including small dots, has been used as prognostic tools to evaluate tumor proliferation levels and troublesome borderline lesions. In this study, NOR patterns of skin cancers were performed in the search of a valuable prognostic method to complement other histological procedures. Paraffin-embedded tumor tissue was obtained from basal and squamous cell carcinomas, cutaneous malignant melanoma, premalignant lesions, and Skmel-28 human melanoma cells. Slices were dewaxed and AgNOR stained. The patterns were scored and submitted for statistical analyses. All types of cancer cells showed variable numbers of abnormally shaped nucleoli and dot-like structures. Only tumor cells presented four or more nucleoli, with or without dots, while 85% of the normal cells had one single NOR without dots. Most data were statistically significant when compared to normal cells. As a whole, squamous cell carcinoma and malignant melanoma tumor cells had less NOR alterations than basal cell carcinoma (BCC) tumor types. Changes in the number and shape of nucleoli present in malignant cells could be attributed to increased levels on rDNA transcription on cancer cells, besides abnormal remodeling of chromatin, which could disrupt proper nucleoli association. Increased genetic alterations on malignant basal cells could contribute to impair invasive and migration abilities of BCC tumors.

Pharmacokinetics and clinical effects of mono‐l‐aspartyl chlorin e6 (NPe6) photodynamic therapy in adult patients with primary or secondary cancer of the skin and mucosal surfaces

Mono-L-aspartyl chlorin e6 (NPe6) is a photosensitizer that exhibits chemical purity, absorption at 664 nm wavelength and may be useful in photodynamic therapy (PDT). This open label phase I clinical trial at the University of California, Davis Medical Center examined the pharmacokinetic properties of Npe6 and clinical response to PDT with this photosensitizer. A single intravenous dose of Npe6 was administered to 14 cancer patients with superficial malignancies (basal cell carcinoma = 22 lesions, squamous cell cancer = 13 lesions, papillary carcinoma = 14 lesions). Patients received one of five ascending doses (0.5 mg/kg (n = 4), 1.0 mg/kg (n = 3), 1.65 mg/kg (n = 3), 2.5 mg/kg (n = 3), or 3.5 mg/kg (n = 1)) 4-8 h prior to light activation. The total light dose (range 25-200 J/cm2) depended on the tumor shape and size. Light was delivered using an argon-pumped tunable dye laser. Serum NPe6 concentrations were measured over a 28-day period. The toxicity and cutaneous clinical efficacy of NPe6 were observed. Four weeks post-PDT, 20 of 22 basal cell carcinoma tumors (91%) showed a complete response. Eighteen of 27 other malignant cutaneous tumors showed a complete (n = 15/27, 56%) or partial (n = 3/27, 11%) response. Fewer non-responders were seen at an Npe6 dose level of 1.65 mg/kg or higher. Only 2 of 14 patients experienced an adverse event that was definitely related to NPe6 administration. Photosensitivity resolved within 1 week of NPe6 dosing in 12 of 14 patients. Analysis of serum levels of 11 individual patients indicated that a two-compartment model with a residual phase best fits the data. The mean alpha, beta, and terminal half-lives were 8.63+/-2.92, 105.90+/-37.59 and 168.11+/-53.40 h (+/-1 SD), respectively. The observed mean volume of distribution was 5.94+/-2.55 l, and the mean clearance was 0.0394+/-0.0132 l/h. These values were independent of the dose administered. The photosensitizer, NPe6, was well tolerated with minimal phototoxic side effects, and demonstrated preliminary efficacy against cutaneous malignancies.

Identification and characterization of rat Desert hedgehog and Indian hedgehog genes in silico

Sonic hedgehog (SHH), Desert hedgehog (DHH) and Indian hedgehog (IHH) bind to Patched family receptors (PTCH1 and PTCH2) to transduce signals to GLI1, GLI2 and GLI3. GLI family transcription factors then activate transcription of Hedgehog target genes, such as FOXE1 and FOXM1 encoding Forkhead-box transcription factors. Hedgehog signaling pathway plays a pivotal role in a variety of human tumors, such as gastric cancer, pancreatic cancer, colorectal cancer, breast cancer, prostate cancer, basal cell carcinoma and brain tumors. Rat orthologs for human DHH and IHH remain to be identified. Here, we identified and characterized rat Dhh and Ihh genes by using bioinformatics. Rat Dhh complete coding sequence (CDS) was determined by assembling nucleotide positions 426397-426963, 429715-429976 and 430244-430898 of the AC114446.3 genome sequence. Rat Ihh complete CDS was determined by assembling nucleotide positions 63433-64033, 66432-66693 and 68242-69169 of AC095777.6 genome sequence. Rat Dhh mRNA was expressed in prostate, duodenum and dorsal root ganglia, while rat Ihh mRNA was expressed in cartilage. Rat Dhh showed 99.7% total-amino-acid identity with mouse Dhh, and 96.5% total-amino-acid identity with human DHH. Rat Ihh and human IHH were shorter than mouse Ihh by 38 amino acids. Rat Ihh showed 97.6% total-amino-acid identity with mouse Ihh and 94.4% total-amino-acid identity with human IHH. Hedgehog family proteins consist of signal peptide, Hedgehog ligand peptide and C-terminal peptide. Hedgehog ligand peptides derived from mammalian Hedgehog family proteins were conserved well, while C-terminal peptides were relatively divergent. The HPLGMXXXXS motif in the C-terminus was conserved in Shh orthologs and Ihh orthologs, but not in Dhh orthologs.

Molecular diagnosis of basal cell carcinoma and other basaloid cell neoplasms of the skin by the quantification of Gli1 transcript levels

Distinguishing basal cell carcinoma (BCC) from other benign and malignant skin tumors is sometimes a difficult task for the pathologists. Because the activation of hedgehog signals and the up-regulation of its critical transcriptional factor Gli1 are well documented in BCC, a molecular technique measuring Gli1 transcripts may aide the diagnosis. Gli1 transcript levels were measured by real-time quantitative reverse transcriptase polymerase chain reaction (RT-PCR) using RNA extracted from formalin-fixed, paraffin-embedded tissues of 68 cases of various skin tumors. Hematoxylin and eosin-stained pathology slides were independently reviewed by three expert dermatopathologists. The histological diagnoses were unambiguous in 53 tumors. The tumors included BCC (21), squamous cell carcinoma (13), seborrheic keratoses (8), trichoepithelioma (5), eccrine poroma/porocarcinoma (4), and sebaceous epithelioma/carcinoma (2). In these unambiguous cases, all BCC and trichoepithelioma tumors showed high expression of Gli1mRNA, while the expression was virtually absent in other tumors. The diagnosis was discordant among three pathologists in the remaining 15 tumors. Histological diagnoses included BCC, BCC with sebaceous differentiation, sebaceoma/sebaceous epithelioma, trichoblastoma, trichoepithelioma, basaloid follicular harmartoma, basosquamous carcinoma, etc. Six of them showed high Gli1 transcript levels. Quantification of Gli1 transcripts by RT-PCR is helpful in discriminating BCC and trichoepithelioma from other skin tumors.

5% Imiquimod Cream and Reflectance-Mode Confocal Microscopy as Adjunct Modalities to Mohs Micrographic Surgery for Treatment of Basal Cell Carcinoma

Imiquimod is an immune response modifier that up-regulates cytokines and has been shown in clinical studies to reduce or clear basal cell carcinoma tumors when applied topically. The objectives were to evaluate the efficacy of 5% imiquimod cream in treating basal cell carcinoma preceding excision by Mohs micrographic surgery and to determine if reflectance-mode confocal microscopy is useful to establish the need for surgical intervention after imiquimod treatment. Subjects applied study cream to one biopsy-confirmed basal cell carcinoma tumor 5 x/week for 2, 4, or 6 weeks in this vehicle-controlled, double-blind study. Confocal microscopy was used for the 6-week treatment group to examine the target tumor area at each interval visit and immediately before Mohs micrographic surgery. After the Mohs micrographic surgery excision, the tissue was evaluated histologically, and the excision area was measured. Confocal microscopy readings were correlated to the histologic diagnosis. Tumors cleared or the target tumor area was reduced in subjects in the 4- and 6-week dosing regimens. Confocal microscopy assessments correlated well with the histologic diagnosis. Imiquimod improved excision results relative to vehicle when used for treating basal cell carcinoma before Mohs micrographic surgery. Confocal microscopy assessments correlated well with tumor response to therapy, suggesting that confocal microscopy may help determine the need for surgery.

5% Imiquimod Cream and Reflectance-Mode Confocal Microscopy as Adjunct Modalities to Mohs Micrographic Surgery for Treatment of Basal Cell Carcinoma

BACKGROUND Imiquimod is an immune response modifier that up-regulates cytokines and has been shown in clinical studies to reduce or clear basal cell carcinoma tumors when applied topically. OBJECTIVE The objectives were to evaluate the efficacy of 5% imiquimod cream in treating basal cell carcinoma preceding excision by Mohs micrographic surgery and to determine if reflectance-mode confocal microscopy is useful to establish the need for surgical intervention after imiquimod treatment. METHODS Subjects applied study cream to one biopsy-confirmed basal cell carcinoma tumor 5 ×/week for 2, 4, or 6 weeks in this vehicle-controlled, double-blind study. Confocal microscopy was used for the 6-week treatment group to examine the target tumor area at each interval visit and immediately before Mohs micrographic surgery. After the Mohs micrographic surgery excision, the tissue was evaluated histologically, and the excision area was measured. Confocal microscopy readings were correlated to the histologic diagnosis. RESULTS Tumors cleared or the target tumor area was reduced in subjects in the 4- and 6-week dosing regimens. Confocal microscopy assessments correlated well with the histologic diagnosis. CONCLUSION Imiquimod improved excision results relative to vehicle when used for treating basal cell carcinoma before Mohs micrographic surgery. Confocal microscopy assessments correlated well with tumor response to therapy, suggesting that confocal microscopy may help determine the need for surgery.

Activation of the BCL2 Promoter in Response to Hedgehog/GLI Signal Transduction Is Predominantly Mediated by GLI2

Aberrant activation of the Hedgehog (HH)/GLI signaling pathway has been implicated in the development of basal cell carcinoma (BCC). The zinc finger transcription factors GLI1 and GLI2 are considered mediators of the HH signal in epidermal cells, although their tumorigenic nature and their relative contribution to tumorigenesis are only poorly understood. To shed light on the respective role of these transcription factors in epidermal neoplasia, we screened for genes preferentially regulated either by GLI1 or GLI2 in human epidermal cells. We show here that expression of the key antiapoptotic factor BCL2 is predominantly activated by GLI2 compared with GLI1. Detailed promoter analysis and gel shift assays identified three GLI binding sites in the human BCL2 cis-regulatory region. We found that one of these binding sites is critical for conferring GLI2-specific activation of the human BCL2 promoter and that the selective induction of BCL2 expression depends on the zinc finger DNA binding domain of GLI2. In vivo, GLI2 and BCL2 were coexpressed in the outer root sheath of hair follicles and BCC and in plasma cells that infiltrated BCC tumor islands. On the basis of the latter observation, we analyzed plasma cell-derived tumors and found strong expression of GLI2 and BCL2 in neoplastic cells of plasmacytoma patients, implicating HH/GLI signaling in the development of plasma cell-derived malignancies. The results reveal a central role for GLI2 in activating the prosurvival factor BCL2, which may represent an important mechanism in the development or maintenance of cancers associated with inappropriate HH signaling.

Cyclooxygenase-2 is a possible target of treatment approach in conjunction with photodynamic therapy for various disorders in skin and oral cavity.

Anti-cancer effects of cyclooxygenase (COX)-2 inhibitors have been reported, but not fully investigated in skin and oral diseases. 5-aminolaevulinic acid (ALA)-based photodynamic therapy (PDT) for treating those patients with skin and oral lesions is a highly sophisticated procedure, but the incidence of disease recurrence after treatment is rather significant. To confirm that COX-2 could be a molecular target in adjunctive therapy to ALA-based PDT, we investigated (i) COX-2 expression in various skin and oral diseases, and (ii) the inhibitory effects on cellular growth of COX-2 selective inhibitor (nimesulide), ALA-based PDT and their combination on human oral squamous cell carcinoma (SCC) cell lines. A total of 129 biopsy samples from the skin and oral mucosal lesions were tested immunohistochemically for COX-2 expression. Then the in vitro effects of nimesulide, ALA-based PDT, and their combination were determined on two SCC cell lines, HSC-2 and HSC-4. Three different methods (MTT assay, double-staining for annexin V and propidium iodide, caspase-3/CPP32 fluorometric protease assay) were applied for evaluation of their inhibitory effects on these two cell lines. Among the skin diseases, a considerable number of COX-2 high expressers were found in actinic keratosis (15 of 25, 60%), Bowen's disease (13 of 17, 76%) and extramammary Paget's disease (15 of 15, 100%). In contrast, only one of 33 (3%) basal cell carcinoma tumours was a COX-2 high expresser. Among the oral mucosal biopsies, the proportion of COX-2 high expressers increased gradually from hyperplasia (one of six, 17%) through mild dysplasia (five of eight, 63%) and moderate dysplasia (20 of 23, 87%) to severe dysplasia (two of two, 100%). Nimesulide had an inhibitory effect in vitro on HSC-2 (proven to be a COX-2 high expresser), but not on HSC-4 (a COX-2 non-expresser). While ALA-based PDT showed an inhibitory effect on both HSC-2 and HSC-4, most importantly the combination of nimesulide and ALA-based PDT demonstrated a significant synergistic effect on the cellular growth inhibition of only HSC-2, but not of HSC-4. Our study strongly suggests that COX-2 can be one of the molecular targets in treating various skin and oral diseases. The results from our in vitro experiments also prompt us to develop a new protocol with a combination of COX-2 selective inhibitor and ALA-based PDT for more effective treatment of those diseases.

GLI2 is expressed in normal human epidermis and BCC and induces GLI1 expression by binding to its promoter.

Sonic hedgehog (Shh) binds to its receptor patched (PTCH), leading to the activation and repression of target genes via the GLI family of zinc-finger transcription factors. Deregulation of the Shh pathway is associated with basal cell carcinoma (BCC) due to upregulation of GLI1 and GLI2. We recently demonstrated a positive feedback loop between GLI1 and GLI2, which revealed that GLI1 may be a direct target of GLI2. Using band shift and luciferase reporter assays, we now show that GLI2 binds the GLI-binding consensus sequence in the GLI1 promoter. These data suggest that GLI2 directly activates GLI1 and that retrovirally expressed GLI2 induces expression of endogenous GLI1 in human primary keratinocytes. Finally, using in situ hybridization, we show that GLI2 is expressed in the interfollicular epidermis and the outer root sheath of hair follicles in normal skin as well as in BCC tumor islands. These results suggest an important role for GLI2 in regulating epidermal proliferation and skin tumorigenesis.

Distinct roles of PTCH2 splice variants in Hedgehog signalling.

The human PTCH2 gene is highly similar to PTCH1, a tumour suppressor gene frequently mutated in basal cell carcinoma and several other tumour types. PTCH1 is a transmembrane protein believed to inhibit another transmembrane protein SMO (Smoothened), which mediates HH (Hedgehog) signalling. In this study, we analysed the biological properties of several PTCH2 splice variants. An mRNA form that lacked the last exon was abundantly expressed in all tissues examined, in contrast with the one that included it. Moreover, a transcript lacking exon 9, which is a part of a conserved sterol-sensing domain, was identified in intestine, prostate and cerebellum. In ovary, spleen, testis, cerebellum and skin, an mRNA lacking both exons 9 and 10 could also be observed. The different PTCH2 isoforms localized in the cytoplasm were capable of internalizing the N-terminal fragment of Sonic HH (Shh-N). Additionally, the PTCH2 gene was found to be a target of HH signalling. PTCH2 promoter regulation assays demonstrated that only one of the PTCH2 variants could inhibit the activity of SHH-N, whereas none was capable of inhibiting the activated form of SMO (SMO-M2) and this contrasts with PTCH1. Despite the fact that the PTCH2 isoforms lacked the ability to inhibit SMO-M2 activity, all PTCH2 variants as well as PTCH1, on co-transfection with Smo, were able to change Smo localization from being largely dispersed in the cytoplasm to the juxtanuclear region. Furthermore, the PTCH2 isoforms and PTCH1 co-localized in doubly transfected cells and an interaction between them was confirmed using immunoprecipitation assays. Using Ptch1-/- mouse cells, it was shown that the PTCH2 variants and PTCH1 differentially act to reconstitute not only the SHH but also the Desert HH-dependent transcriptional response. We conclude that in spite of their structural similarities, the PTCH2 isoforms have distinct functional properties when compared with PTCH1.